ARMOURDOWEL is a plate dowel/load transfer system designed speci cally to meet the demanding needs of today’s industrial concrete floors. ARMOURDOWEL surpasses the requirements of TR34 3rd Edition. ARMOURDOWEL stands for superior performance through innovative design.
ARMOURDOWEL leads the way with a unique and revolutionary ‘asymmetrical dowel’. Most other traditional joint systems are designed such that the dowel is positioned central across the joint when the joint is closed. From the moment thejoint opens, dowel engagement on the free side reduces, thus moving away from a condition of equal dowel engagement on both sides of the joint. Ultimately, with large joint openings there is a risk of the dowel becoming totally disengaged on the free side, the complete loss of load transfer across the joint and a failed oor. ARMOURDOWEL works differently. As the joint opens, ARMOURDOWEL moves towards a condition of equal dowel engagement. Even at a maximum joint opening of 30mm, each side of the joint has a class leading 60mm of dowel engagement. ARMOURDOWEL’S are made from a high grade S355 steel (355N/mm2 yield strength), 150mm x 150mm square and either 8mm or 12mm thick. The dowel thickness and spacing must be determined by the slab designer.
! Please note all opened joints must be lled with a suitable sealant to reduce the impact from traf c across the joint. This sealant must be periodically repaired or replaced as required in order to maintain joint service life.
- Mark out the timber formwork with a centreline at half depth and the correct spacings.
- Screw the plastic insert to the timber formwork at half the depth of the slab. Space the inserts at the recommended distances to achieve the load transfer requirement as speci ed by the slab designer. Ensure that inserts are both horizontal and true. If the inserts are tted at an angle then the sleeves when tted will also be at an angle and this will cause slab lock-up and cracking may occur.
- Once all of the inserts have been screwed to the timber formwork, fit the sleeves. These can be nailed in place too if required.
- Then cast the slab and ensure the concrete is compacted with a vibropoker along the slab edges and around the sleeves. Take care not to hit the sleeves with the vibro-poker or they may become dislodged. Allow the concrete to cure. Remove the timber formwork carefully. The inserts will still be attached to the timber formwork and can be used again.
- Fit the dowel in to the sleeve such that it is fully engaged (approx 60mm of dowel should be protruding) and ensure the dowel is central (20mm space either side of the dowel).
- Cast the adjacent slab.
The sleeve’s purpose is to form a barrier between the steel dowel and the concrete and allow the concrete to release in two horizontal planes (parallel to the joint and perpendicular to the joint) on the free side of the joint.
Vertical displacement between adjacent slab panels is undesirable as this can lead to a reduction in oor and joint life. ARMOURSLEEVES are designed to allow up to ± 20mm parallel movement along the joint before the joint opens up. Other dowel systems allow zero parallel movement between slab panels (i.e. along deck levellers) and can cause slab lock-up. The long term performance of a concrete oor is highly dependent upon the quality and performance of the joint system.
The ultimate load transfer is the theoretical maximum load transfer that can be experienced by a oor joint up to the point at which either the concrete or dowel starts to fail. It is necessary to determine the ultimate load transfer for each slab design
in order to ensure the required maximum working load will not exceed the ultimate load. In most situations, at the point of ultimate load, the concrete would typically fail before the dowel. The concrete may fail in two ways; bursting or bearing (which is far less likely). Bursting (a tensile failure of the concrete) is where the dowel breaks out of the slab and the concrete is ruptured. Bearing is where the concrete fails due to compression under the surface of the dowel when loaded. Failure of the dowel can be in three forms; bending, shear or combined bending and shear. Bending is where the dowel becomes overloaded and bends, beyond it’s elastic limit, across the joint. Shear is where the dowel fails to carry the load across the joint and starts to shear at the joint. Combined bending and shear, as it’s name suggests, is a combination of both failure modes. The ultimate load transfer across a oor joint is dependent upon a number of factors; the shape and size of the dowel, the strength of the dowel materials, the concrete strength, the size of the joint opening etc.
It is possible to theoretically calculate the ultimate load at the joint using the methods set out in TR34 3rd Edition.
The table above summarises the limit of load transfer for various slab thickness where 32N/mm2 cylindrical strength concrete has been used and a long term joint opening of 20mm is anticipated.
Isedio Limited can assist with determining the ultimate load transfer for any given slab design.
ARMOURDOWELS are available in either 8mm thickness or 12mm thickness and are usually spaced at 600mm centres.
The 12mm dowel can transfer a higher load but is only required on thicker slabs with heavydosages of steel bre reinforcement or slabs on piles.
! Please note that the engineer responsible for the oor slab design must check that the required maximum working load transfer across the joint does not exceed the ultimate load transfer capacity.